The above-identified applications and patents are the closest known prior art. The electrodes involved in such apparatus were described as needle electrodes and, in any event, were electrode elements of pointed or small diameter tip configurations with the electrodes fixed to a common base. It has been demonstrated that production of corona discharge for cooking and other heating applications is most efficiently accomplished by employing so-called "needle" electrode arrays for the active corona generator part of the electrode. However, when this is done various problems exist. The exposed pointed tips of the exposed needle electrodes are a potential source of injury to the user. The exposed needles are also subject to damage by the user which could reduce the electrode's effectiveness. Further, the needle electrode array in its support structure present a serious problem with regard to cleaning.
It is possible, of course, to devise mechanical means for preventing or making unlikely the injury of the user or the damage of the needles. It is even possible to reduce the cleanability problem somewhat. However, for solutions of this sort, complicated mechanisms which add cost to the unit are required. The cost is increased if the solution provided involves mechanical means which requires some sort of automatic actuation.
The present invention allows a solution to the aforementioned problem without mechanical additions which add expense or complication to the structure and without affecting the performance qualities of the device. In fact, the present invention permits reduction in cost.
The present invention provides a solution which retains all of the needed electrical qualities but eliminates the mechanical quality of rigidity which is primarily responsible for the difficulties described. In short, the active corona generator of the electrode device are designed to be mechanically flexible. While the elements remain pointed, the property of flexibility allows them to temporarily yield rather than either injuring the user or damaging something introduced by the user into the oven or else permanently bending in such a way as to reduce their effectiveness. The electrodes of the present invention, after yielding upon contact, are free to return to effective position and, moreover, are drawn by the electrostatic forces into effective position when in operation.
Additionally, the corona generators, in accordance with the present invention, are to an important extent self-adjusting. Because they are flexible, the corona generators are able to adjust individually to maintain common potential at the various electrode needles. For example, when food in a metal pan is introduced, those electrodes over the edge of the pan will receed. Even changes in the shape of food during cooking may cause a change in the "profile" of the corona generators such that different ones withdraw differing amounts corresponding to keep their distance above the food surface constant and uniform as baked goods rise, for example.
More specifically, the present invention relates to an improved electrode configuration for use in an oven for cooking food employing corona discharge as a means for enhancing heat and mass transfer. The electrode configuration employs a plurality of corona generators with pointed or small diameter free ends fixed to a common conductive sheet at their opposite ends to generate a corona discharge between that electrode and another body providing an electrode when a corona generating field is introduced between the electrodes. The improved electrode configuration comprises use of flexible electrodes having at least a metallic surface and connected to the conductive sheet so as to yield under pressure but return to operative position upon imposition of the corona producing field .